This invention relates to a photographic printing apparatus wherein images are printed from a negative onto a strip of photographic printing paper and the strip is then transferred to a developing apparatus.
Various methods are known for harmonizing the speed of intermittent printing with that of continuous development in order to feed a developing apparatus with a strip of photographic printing paper after it has been printed. These methods may be roughly classified into methods in which a strip of printed paper is cut into sheets, each defining an independent frame, and is transferred to the developing apparatus, and methods in which a strip of printed paper is fed directly to the developing apparatus. The former method, however, requires a complicated mechanism including many rollers for transporting sheets of printing paper into the developing apparatus, since the printing paper is less rigid than the negative, though it can satisfactorily harmonize the speeds of printing and developing. According to the latter method, it is sufficient to use a simpler mechanism, which may be a leader or a chain-driven clip engaged with the leading edge of the strip, but there remain difficulties in harmonizing the printing and developing speeds. It is sometimes necessary to cut the printed portion of the strip from the unprinted portion.
While the developing device is usually stationary, the printing device is sometimes vertically movable for varying the distance between the light source and the developing table. The vertical movement of the printing device naturally causes a change in the distance between the printing and developing devices. There has, therefore, been a need for a mechanism enabling expansion and contraction of the chain conveyors in accordance with the varying distance between the printing and developing devices.
There is known a rod-shaped guide clip to which the leading edge of a strip of printed photographic paper is connected, and which is engaged at both ends with chain conveyors, or like means moving through a developing tank in which the photographic paper is printed.
A guide clip is set in a predetermined standby position, and a strip of photographic paper is conveyed. When the leading edge of the strip has reached the aforesaid predetermined position, the strip is connected with the guide clip. The presence of various machine parts in the vicinity of the guide clip standby position, however, makes it very difficult to set the guide clip in position manually. After the strip has been conveyed by the guide clip, it is necessary to set another guide clip in a standby position to receive any convey another strip of paper into the developing tank. It has, therefore, been desired to develop a mechanism for automatically guiding a guide clip to a standby position whenever required.